1. Field of the Invention
The present invention relates to an image forming apparatus for image formation on tabbed sheets, and a control method therefor.
2. Description of the Related Art
Conventionally, some image forming apparatus comprises a tabbed sheet creation mode in which tabbed sheets are formed with corresponding images.
The tabbed sheet creation mode will be described with reference to FIGS. 18A-21. FIGS. 18A and 18B show how tabbed sheets are arranged in a tabbed sheet group, which consists of seven tabbed sheets. FIG. 19 schematically shows how a plurality of tabbed sheet groups are loaded on a sheet feed tray of an image forming apparatus. FIG. 20 shows an example of image formation on two tabbed sheets by using a tabbed sheet group consisting of seven tabbed sheets. FIG. 21 shows an example of image formation on nine tabbed sheets by using a plurality of tabbed sheet groups each consisting of seven tabbed sheets.
As shown for example in FIG. 18A, there is on the market a tabbed sheet group consisting of seven tabbed sheets having respective tabs formed therein at different positions. In this tabbed sheet group, tabbed sheets are arranged in a decreasing order of tab position. Besides, there is a tabbed sheet group consisting of tabbed sheets arranged in an increasing order of tab position, as shown in FIG. 18B.
When loaded onto a sheet feed tray of an image forming apparatus, the tabbed sheet groups are loaded on a per-group basis as shown in FIG. 19. In the example in FIG. 19, there are loaded on the tray a plurality of tabbed sheet groups each of which corresponds to the tabbed sheet group shown in FIG. 18A.
At the image formation on the first two of seven tabbed sheets of the tabbed sheet group, the first two tabbed sheets P1-P2 are respectively formed with corresponding images “1” and “2” as shown in FIG. 20. The remaining five tabbed sheets P3-P7 are not fed, but remain retained as surplus tabbed sheets in the sheet feed tray.
As described above, the number of tabbed sheets formed with images is sometimes less than the number of tabbed sheets constituting the tabbed sheet group, and surplus tabbed sheets remain in the sheet feed tray. A technical art has therefore been proposed for discharging surplus tabbed sheets to a sheet discharge tray different from that for tabbed sheets formed with images (see, for example, Japanese Laid-open Patent Publication No. 2002-3063).
It is assumed here that a plurality of tabbed sheet groups each consisting of, e.g., seven tabbed sheets are loaded onto a sheet feed tray, and images are formed on respective ones of the first two tabbed sheets. In this case, two tabbed sheets of the first tabbed sheet group are fed in sequence and respectively formed with corresponding images. The tabbed sheets formed with the images are discharged to a first sheet discharge tray. The remaining five tabbed sheets of the first tabbed sheet group are discharged as surplus tabbed sheets to a second sheet discharge tray different from the first sheet discharge tray.
When image formation for a second set is performed in succession to the image formation for a first set, the first two of tabbed sheets of a second tabbed sheet group are respectively formed with corresponding images, and the tabbed sheets formed with the images are discharged to the first sheet discharge tray. The remaining five tabbed sheets are discharged as surplus tabbed sheets to the second sheet discharge tray.
It is assumed here that a plurality of tabbed sheet groups each consisting of seven tabbed sheets are loaded onto the sheet feed tray, and a setting for image formation on nine tabbed sheets is performed by a user. In this case, as shown in FIG. 21, the first to seventh tabbed sheets P1-P7 of the first tabbed sheet group are formed with corresponding images “1” to “7”. In succession, images “8” and “9” are respectively formed on the first two P8, P9 of tabbed sheets of the second tabbed sheet group. The tabbed sheets P1-P9 are discharged to the first sheet discharge tray. On the other hand, the remaining five tabbed sheets P10-P14 of the second tabbed sheet group are discharged as surplus tabbed sheets to the second sheet discharge tray.
In the case of producing plural sets of output, surplus tabbed sheets are discharged in each set of output as described above, resulting in a large number of surplus tabbed sheets. In some cases, surplus tabbed sheets produced in each set of output include tabbed sheets that can be sorted for reutilization for the next set of output. In that case, a tabbed sheet group can be reconstructed by the user by sorting the surplus tabbed sheets.
However, to reutilize a reconstructed tabbed sheet group for the next set of output, the user is required to reconstruct a tabbed sheet group using reusable surplus tabbed sheets and load the reconstructed tabbed sheet group onto a sheet feed tray after each set of output, which is quite laborious.